Vehicles equipped with respective automatic transmissions have heretofore been sold. Some of the automatic transmissions automatically shift gears and additionally allow a driver to select a gear ratio (gear) by shift operation of the driver in order to shift gears as intended by the driver. The gear shifting by the driver's shift operation is effected by selection of a shift range that allows gear shifting to be done within a predetermined shift range or by selection of a gear.
Japanese Patent Laying-Open No. 2001-200929 discloses an operation device for an automatic transmission that can change the shift range. The operation device for an automatic transmission disclosed in Japanese Patent Laying-Open No. 2001-200929 is an operation device for an automatic transmission capable of setting the shift range by operation of a select lever supported on a lateral side of a vehicle seat. The operation device includes a main gate guiding the select lever to range positions corresponding respectively to P, R, N and D ranges, a sub gate that is a sub gate extending from the range position of the D range in the main gate in the vehicle's width direction and guiding the select lever to a shift-range changing position located near an end of the sub gate, a first detection switch that is made ON by driver's operation and a second detection switch configured separately from the first detection switch, and a control unit controlling the automatic transmission based on the operation of the select lever in the main gate as well as the first and second detection switches. The control unit controls the automatic transmission so that the shift range which determines the gear-shifting range of the automatic transmission is changed to a shift range of a wider gear-shifting range each time the first detection switch is made ON and so that the shift range is changed to a shift range of a narrower gear-shifting range each time the second detection switch is made ON.
Regarding the operation device disclosed in the above-referenced publication, driver's operation can cause the shift range which determines the gear-shifting range of the automatic transmission to change, from the state where the select lever is changed in position to the shift-range changing position, to a shift range of a wider gear-shifting range or a shift range of a narrower gear-shifting range, each time the first or second detection switch is made ON.
As for an automatic transmission configured with a planetary gear unit, there is a neutral state in which the output-shaft torque of the automatic transmission is substantially zero, between engagement and disengagement of frictional engagement elements of the automatic transmission when gear shifting is done. Therefore, even if a driver performs manual shift to downshift the automatic transmission for the purpose of effecting engine brake, a braking force as intended by the driver may not be obtained. Therefore, a technique has been proposed according to which a braking force is applied in the manual shift mode.
Japanese Patent Laying-Open No. 63-038060 discloses a brake control device for a vehicle that can provide a stable braking force in the manual shift mode. The brake control device for a vehicle disclosed in Japanese Patent Laying-Open No. 63-038060 includes manual shift detection means for detecting that the mode is the manual shift mode of an automatic transmission for effecting engine braking, engine load detection means for detecting the engine load, and brake drive means for operating a vehicle's brake to a predetermined extent for a predetermined time when the mode is the manual shift mode and the engine load is not more than a predetermined value.
Regarding the brake control device disclosed in the above-referenced publication, when the mode is the manual shift mode and the engine load is not more than a predetermined value, the brake drive means operates the vehicle's brake to a predetermined extent for a predetermined time. Thus, in the case where the mode is the manual shift mode in which manual shift is performed requiring engine braking and the automatic transmission is in the neutral state, the vehicle's brake is operated. In this way, a braking force can be exerted on the vehicle in the manual shift mode.
In the case of the operation device disclosed in Japanese Patent Laying-Open No. 2001-200929, however, when the shift range is changed for example from the 5 range in 3rd gear to the 4 range or 3 range, the gear is kept in 3rd gear. In this case, the braking force generated by the engine brake cannot be obtained. Therefore, there is a problem here that perceived deceleration as intended by the driver cannot be obtained.
In the case of the brake control device disclosed in Japanese Patent Laying-Open No. 63-038060, unless the automatic transmission is in the neutral state while gear shifting is done, the braking force generated by the brake cannot be obtained. If gear shifting is not done, the neutral state does not occur. Therefore, like the case of the operation device disclosed in Japanese Patent Laying-Open No. 2001-200929, the braking force generated by the engine brake cannot be obtained when the gear is maintained in the manual shift mode. Further, if the automatic transmission is a CVT (Continuously Variable Transmission), the transmission does not become the neutral state while shifting is done and thus the braking force generated by the brake cannot be obtained. Therefore, there is a problem here that perceived deceleration as intended by the driver cannot be obtained.